Potential-tap assembly for relatively high-voltage equipment



April 14, 1964 J. H. FRAKES ETAL 3,129,310

POTENTIAL-TAP ASSEMBLY FOR RELATIVELY HIGHVOLTAGE EQUIPMENT Filed June 1, 1961 James H. Frokes and Robert E. Friedrich.

3 1 BY $44M A. M

j ATTORNEY United States Patent 3,129,310 POTENTIAL-TAP ASSEMBLY FOR RELATIVELY HIGH-VOLTAGE EQUIPMENT James H. Frakes, Penn Township, Allegheny County, and

Robert E. Friedrich, Pittsburgh, Pa., assiguors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed June 1, 1961, Ser. No. 114,145 5 Claims. (Cl. 200-148) This invention relates to potential-tap assemblies for relatively high-voltage equipment in general, and, more particularly, to potential-tap assemblies for relatively highvoltage equipment encompassing the high-voltage lead for such equipment.

In the operation of relatively high-voltage equipment, say of the order of 46 kv. and upwards, it is frequently desirable to provide a means for securing small amounts of power from high-voltage lines. Potential devices, commonly used, provide a relatively low-voltage output which is substantially proportional to the system line-to-ground voltage, and is in phase with it. This output is commonly used to energize synchroscopes, voltmeters, and voltageresponsive relays. Such devices provide effective means of obtaining potential to operate relays, indicating instruments, and synchronizing devices.

Accordingly, it is a general object of the present invention to provide an improved potential-tap assembly for relatively high-voltage equipment to operate potential devices and the like.

A more specific object of the present invention is the provision of an improved potential-tap device which is compact in size, readily assembled in the equipment, economical to manufacture, and which is effective and accurate in operation.

Another object of the present invention is the provision of an improved potential-tap device for a power circuit breaker which may be readily assembled within the tank neck adjacent the supported terminal bushing.

An ancillary object of the invention is to provide an improved potential-tap device comprising an electricallyfloating potential cylinder disposed interiorly of the supporting neck portion of a grounded-tank, gas-filled power circuit breaker, which will not be disturbed by, nor interfere with, assembly and disassembly of the associated gasfilled terminal bushing.

In United States patent application filed December 2, 1959, Serial No. 856,775, by Robert E. Friedrich and James H. Frakes, now United States Patent 3,059,044, issued October 16, 1962, and assigned to the assignee of the instant application, there is disclosed and claimed the concept of utilizing an interiorly-disposed potential cylinder in a gas-filled terminal bushing. A disadvantage of incorporating the potential cylinder interiorly of the terminal bushing is that should a utility customer initially not desire the potential cylinder and associated potential-tap assembly, and then later, for some reason, change his mind and desire such a device it is then necessary to completely disassemble the gas-filled terminal bushing of the aforesaid application and incorporate the interiorly-disposed potential cylinder therein. Accordingly, it is a further object of the present invention to provide an exteriorly-disposed potential cylinder for a terminal bushing, preferably one of the gas-filled type, which may be easily added to the electrical equipment at a time subsequent to the time of initial installation without added expense and involving little additional labor time.

Briefly stated, this invention provides a potential cylinder insulatedly mounted within the tank neck of the grounded tank encasing such electrical equipment, such as a gas-filled power circuit breaker, with the potential cylinder disposed radially outwardly of the terminal bushice ing extended into the tank structure and disposed within the neck portion of the tank. A small proportion of the line-to-ground voltage will be capacitively picked up by the potential cylinder, and a potential connection may be insulatedly passed laterally through the tank neck to electrically contact the potential cylinder and thereby transmit this small proportion of line-to-ground voltage to an externally-situated potential device for the operation of the same.

Further objects and advantages will readily become apparent upon reading the following specification, taken in conjunction with the attached drawing, in which:

FIGURE 1 is a fragmentary side elevational view, partially in section, of a gas-filled high-power circuit interrupter illustrating an embodiment of the present invention;

FIG. 2 is an enlarged fragmentary view of the potential cylinder of FIG. 1 and the support therefor;

FIG. 3 is an enlarged sectional view of the potentialtap connector assembly making abutting electrical contact with the potential cylinder; and,

FIG. 4 is an enlarged exploded partial view of the potential-tap connector assembly of FIG. 3 which makes an abutting engagement with the potential cylinder.

Referring to the drawing, and more particularly to FIG. 1 thereof, the reference numeral 1 generally designates a gas-filled power circuit interrupter adapted for a voltage and kva. rating of say 138 kv., 10,000 mva. Reference may be had to United States patent application filed January 23, 1959, Serial No. 788,668, by Russell N. Yeckley, Joseph Sucha and Benjamin P. Baker, now United States Patent 3,057,983, issued October 9, 1962, and assigned to the assignee of the instant application, for a detailed description of the operation of the power circuit breaker 1.

For the purpose of understanding the present invention, however, it is only necessary to know that the circuit interrupter 1 comprises a grounded metallic tank structure 2 including a generally elongated grounded metallic central portion 3, a removable end cap 4 and an upstanding cylindrical, or neck supporting portion 5 for mounting the terminal bushing 6 in an upstanding manner, as shown in FIG. 1.

Actually, although not illustrated in FIG. 1, there is provided a pair of downwardly-extending terminal bushings 6 having terminal studs 7 extending axially therethrough. The two terminal bushings 6 support, in a generally horizontal position, an elongated arc-extinguishing assembly 9. Generally, the arc-extinguishing assembly 9 includes a high-pressure reservoir 10 and a plurality of serially-related arc-extinguishing units, not shown. Each arc-extinguishing unit has a pair of separable contact structures and an insulating orifice-shaped interrupter, which receives a blast of high-pressure gas, such as sulfur hexafluoride (SP gas, at a pressure of, say 250 p.s.i., by the operation of suitably synchronously-actuated blast-valve means, not shown associated with highpressure reservoir tank 10.

In the aforesaid United States Patent 3,059,044, there is illustrated and claimed a potential cylinder extending interiorly within the terminal bushing itself adjacent the ground flange. As set forth in this patent, the terminal bushing generally comprised a bare conductor terminal stud extending axially through the bushing, with sulfur hexafluoride (SF gas providing the requisite dielectric strength between the conductor stud and the grounded supporting flange portion, with the SF gas being obtained from the general interior of the associated circuitinterrupter tank.

As stated hereinbefore, occasionally utility customers changed their minds and desired such a potential-cylinder construction at a later date than the date of the initial installation; and it is, with the construction set forth in the aforesaid Patent 3,059,044, then necessary to entirely disassemble the terminal bushing and to incorporate therein the interiorly-disposed potential cylinder into place. This constitutes a major assembly operation, as far as the terminal bushing is concerned.

It is a distinct advantage of the present invention to eliminate such a disassembly step and to provide an exteriorly-disposed potential cylinder, which is positioned within the neck portion of the tank structure 2, such as illustrated in FIG. 1.

With reference to FIG. 2 of the drawings, it will be observed that the metallic cylindrically-shaped potential cylinder 11 is insulated from the mounting flange ring 12, constituting the upper extremity of the neck portion 5, by a plurality, in this particular instance four, insulating bracket straps 14 secured by machine bolts 15, 15 adjacent the upper edge 11a of the potential cylinder 11 and to the lower surface 17 of the flange ring 12. To prevent any contact whatsover of the lower portion of the potential cylinder 11 with the neck portion 5, preferably insulating rivets 18 are provided in spaced relation about the lower edge 11b of the metallic cylindrical potential shield 11. Preferably, the potential cylinder 11 is formed from an elongated rectangular strip of a suitable material, such asaluminum, rolled into a round cylinder and welded along the two abutting end edges.

The terminal bushing 6 includes the axially extended bare terminal stud 7 with a pair of porcelain shells 6a, 612. An intermediately disposed ground flange ring 60, having circumferentially spaced mounting holes, is bolted by bolts 6d to the flange ring 12. Dielectric gas, such as SP fills the free space between the bare terminal stud 7 and the interior surfaces of the porcelain shells 6a, 6b. The construction is generally similar to that of the terminal bushing disclosed in the aforesaid patent application Serial No. 85 6,775, by Friedrich and Frakes.

In order to obtain a transmission of the tapped voltage through the neck portion 5 of the tank 2, a potential-tap connector assembly 19, such as illustrated in FIG. 3, is provided. With reference to FIGS. 3 and 4, it will be noted that there is provided an insulating bushing 20 having a conducting stud 21 passing therethrough in a sealed manner. The bushing 20 has a flanged collar 2% soldersealed thereto in a hermetic fashion, as shown more clearly in the exploded view of FIG. 4. Abutting the inner end of the stud 21 is a plunger contact 23, which makes abutting and telescopic engagement with a conducting compression spring 24, as shown more clearly in FIG. 4. As shown, the conducting compression spring 24 makes abutting engagement, as at 25, with the external side-wall portion 26 of the potential cylinder 11.

The metallic flange portion 20b of the bushing 20 is assembled with a sealing gasket 30 within an apertured supporting plate 31. The latter is, in'turn, mounted by a plurality of bolts 32 to a supporting block 33 welded, as at 34, to the neck portion 5 of the tank 2; An insulating guide tube 38 is disposed within the bore 39 of the apertured supporting block 31. It has at least two func-' tions, first to guide the compression spring 24, and secondly to insulate the current path from the potential cylinder 11 to ground by way ofsupporting block 31. Suitable connector nuts 40 'clampingly engage a potential cable 41 with a potential device 42 (FIG. 1).

From the foregoing description, it will be apparent that the novel potential cylinder 11 of the present invention takes up little space within the neck portion 5 of the tank 2, is readily assembled, and will not interfere with removal of the terminal bushing 6.

The potential cylinder 11 capacitatively takes an electrical charge from the voltage on the terminal bushing 6; Voltage and amperes from the electrical charge are used to operate the potential device 42 for metering purposes.

With the potential device construction illustrated, a.

short height bushing flange 6c may be employed in connection with the terminal bushing 6, such as illustrated in FIG. 1. This allows the terminal bushing 6 to be reduced in height, which reduces cost, gives better electrical characteristics, and lowers the overall circuit breaker heightthat gives an advantage for shipping the breaker 1 completely assembled. The bushing diameter can also be made smaller since room is not needed for an interiorly-disposed potential-tap cylinder, such as set forth in the aforesaid patent application Serial No. 856,775.

The potential-tap is accessible within the tank neck 5 g in case it needs repair. To repair the potential-tap within the terminal bushing 6 requires dismantling the bushing, which is a time-consuming; costly operation.

Another advantage of having a potential-tap within the tank neck 5 is that it can be omitted from orders not calling for a potential device, and added later in the field, if needed. Because of the complicated assembly and major operation, the practice has been to make all bushings with interiorly-disposed potential-taps whether they used the potential device or not. This has been an expensive procedure in the past to follow. 7

By way of example only, and not by way of limitation, for a 138 kv., three-phase power circuit breaker with an interrupting rating of 10,000 mva., the line-to-ground voltage would be approximately kv. and, for example, the voltage on the potential shield 11 (if maintained electrically floating) would be approximately 3000 volts with respect to ground. But if used with a potential device 42 the voltage would be only a small fraction of this value, say 5 or 6 volts with a 0.015 microfarad condenser permanently connected between the potential tap stud 21 and ground.

Although there has been illustrated and described a particular embodiment of the invention, it is to be clearly understood that the same was merely for the purpose of illustration, and that changes and modifications may readily be made therein by those skilled in the art, with out departing from the spirit and scope of the invention.

We claim as our invention:

1. A potential-tap assembly for relatively high-voltage equipment including a conducting potential cylinder,

grounded supporting means for said conducting poten-.

tial cylinder, means insulating said potential cylinder from said grounded supporting means, an independent highvoltage terminal bushing for said relatively high-voltage equipment extending through said potential cylinder and constituting a separate entity, a potential connector for said potential cylinder, and means insulating said potential connector from the grounded supporting means.

2. In combination, tank-mounted relatively high-voltage equipment including a terminal bushing extending into a grounded tank, an independent conducting potential cylinder at least partially encompassing said terminal bushing and constituting a separate entity, means insulating said potential cylinder from the tank, and voltage-tap connecting means making electrical connection to said conducting potential cylinder.

. 3. A potential-tap assembly for a gas-filled power circuit breaker having a tank-mounted terminal bushing, said potential-tap assembly including a conducting potential' cylinder positioned interiorly of the tank, yet constituting a separate entity distinct from said terminal bushing, said potential-tap assembly surrounding the terminal bushing, a potential-tap connector assembly comprising the grounded tank, and the terminal bushing extending in spaced relation through said potential cylinder and being a separate independent part therefrom.

5. A gas-filled power circuit breaker including a grounded elongated tank having at least one upstanding eylindrically-shaped neck portion, a terminal bushing of the gas-filled type extending through said neck portion, an arcextinguishing assemblage supported by the interior end of said terminal bushing, a potential cylinder supported in insulating fashion Within said neck portion, said terminal bushing extending through said potential cylinder and being a separate independent part therefrom, and a poten- 6 tial-tap connector extending laterally through said neck portion and making electrical contact with said potential cylinder.

References Cited in the file of this patent UNITED STATES PATENTS 1,788,873 Jansson Jan. 13, 1931 1,873,977 Naef Aug. 30, 1932 2,889,395 Frakes June 2, 1959 2,916,723 Cronin Dec. 8, 1959 2,937,359 Cronin et al May 17, 1960 3,059,044 Friedrich et al Oct. 16, 1962 

2. IN COMBINATION, TANK-MOUNTED RELATIVELY HIGH-VOLTAGE EQUIPMENT INCLUDING A TERMINAL BUSHING EXTENDING INTO A GROUNDED TANK, AN INDEPENDENT CONDUCTING POTENTIAL CYLINDER AT LEAST PARTIALLY ENCOMPASSING SAID TERMINAL BUSHING AND CONSTITUTING A SEPARATE ENTITY, MEANS INSULAT- 